We measured pre- and postoperative CEA level in 330 patients who underwent resection for lung cancer at Kyushu Cancer Center Hospital between 1983 and 1986 using RIA method. There were 93 patients with high preoperative serum CEA level above 5 ng/ml. The interrelationships among preoperative serum CEA level, prognostic factors, outcome, and postoperative change of CEA level were investigated in the 93 patients. Five-year survival rate of patients with preoperative serum CEA level ranging from 5.0 to 10.0 ng/ml (N = 53) was 60.0%, while that of patients with preoperative CEA level over 10.1 ng/ml (N = 40) was 24.6% (P less than 0.05). Recurrent rate was higher in patients with preoperative CEA level over 10.1 ng/ml, especially in those with lung cancer at stages I or II. However, patients with preoperative CEA level about 50 ng/ml, showed good outcome after curative resection. All 12 patients in whom postoperative serum CEA level did not return to normal died within 4 years, indicating that normalization of CEA level is an important factor in prognosis. This study indicates that among lung cancer patients with high serum CEA level, the preoperative CEA level and postoperative change of CEA level are apparently prognostic factors.